Aftershocks are smaller earthquakes that follow the main shock and can cause further damage to weakened buildings. Aftershocks can occur in the first hours, days, weeks, or even months after the quake. Some earthquakes are actually foreshocks that precede a larger earthquake.
Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric, and telephone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive, seismic sea waves called tsunamis. Buildings with foundations resting on unconsolidated landfill and other unstable soils are at increased risk of damage. Also, mobile homes and homes not attached to their foundations are at particular risk because they can be shaken off their foundations during an earthquake. When an earthquake occurs in a populated area, it may cause deaths and injuries and extensive property damage.
The Northridge, California, earthquake of January
17, 1994, struck a modern urban environment generally designed to withstand the
forces of earthquakes. Its economic cost, nevertheless, was estimated at $20
billion. Fortunately, relatively few lives were lost. Exactly one year later,
Kobe, Japan, a densely populated community less prepared for earthquakes than
Northridge, was devastated by one of the most costly earthquakes ever to occur.
Property losses were projected at $96 billion, and at least 5,378 people were
killed. These two earthquakes tested building codes and construction practices,
as well as emergency preparedness and response procedures.
the damage caused by earthquakes is predictable and preventable. We must all
work together in our communities to apply our knowledge to enact and enforce
up-to-date building codes, retrofit older unsafe buildings, and avoid building
in hazardous areas, such as those prone to landslides. We must also look for
and eliminate hazards at home, where our children spend their days, and where
we work. And we must learn and practice what to do if an earthquake occurs.
If you are at risk from earthquakes, you should:
• Discuss with members of your household the possibility of earthquakes and what to do to stay safe if one occurs. Knowing how to respond will help reduce fear.
• Pick "safe places" in each room of your home and your office or school. A safe place could be under a piece of furniture, such as a sturdy table or desk, or against an interior wall away from windows, bookcases, or tall furniture that could fall on you. The shorter the distance to your safe place, the less likely it is that you will be injured by furnishings that become flying debris during the shaking. Injury statistics show that persons moving as little as 10 feet during an earthquake's shaking are the most likely to experience injury.
• Practice drop, cover, and hold on in each safe place. Drop to the floor, take cover under a sturdy piece of furniture, and hold on to a leg of the furniture. If suitable furniture is not nearby, sit on the floor next to an interior wall and cover your head and neck with your arms. Responding quickly in an earthquake may help protect you from injury. Practice drop, cover, and hold on at least twice a year.
• Keep a flashlight and sturdy shoes by each person’s bed.
• Talk with your insurance agent about earthquake protection. Different areas have different requirements for earthquake protection. Study the locations of active faults, and, if you are at risk, consider purchasing earthquake insurance.
• Inform guests, babysitters, and caregivers of earthquake plans. Everyone in your home should know what to do if an earthquake occurs, even if you are not there at the time.
• Make sure your home is securely anchored to its foundation. Depending on the type of construction and the materials used in building your home, you may need to have it bolted or secured in another way to its foundation. If you are not sure that your home is securely anchored, contact a professional contractor. Homes securely attached to their foundations are less likely to be severely damaged during earthquakes, and become uninhabitable.
• Bolt and brace water heaters and gas appliances to wall studs. If the water heater tips over, the gas line could break, causing a fire hazard, and the water line could rupture. The water heater may be your best source of drinkable water following an earthquake. Consider having a licensed professional install flexible fittings for gas and water pipes.
• Bolt bookcases, china cabinets, and other tall furniture to wall studs. Brace or anchor high or top-heavy objects. During an earthquake, these items can fall over, causing damage or injury.
• Hang heavy items, such as pictures and mirrors, away from beds, couches, and anywhere people sleep or sit. Earthquakes can knock things off walls, causing damage or injury.
• Brace overhead light fixtures. During earthquakes, overhead light fixtures may fall, causing damage or injury.
• Install strong latches or bolts on cabinets. The contents of cabinets can shift during the shaking of an earthquake. Latches will prevent cabinets from opening and spilling out the contents. Place large or heavy objects on shelves near the floor.
• Secure large items that might fall and break (televisions, computers, etc.).
• Store weed killers, pesticides, and flammable products securely in closed, latched metal cabinets.
• Evaluate animal facilities and places your pets like to hide in, to ensure that any hazardous substances or structures are as safe as possible.
• Consider having your building evaluated by a professional structural design engineer. Ask about home repair and strengthening tips for exterior features, such as porches, front and back decks, sliding glass doors, canopies, carports, and garage doors. This is particularly important if there are signs of structural defects, such as foundation cracks. Earthquakes can turn cracks into ruptures and make smaller problems bigger. A professional can give you advice on how to reduce potential damage.
• Follow local seismic building standards and land use codes that regulate land use along fault lines, in areas of steep topography, and along shorelines. Some municipalities, counties, and states have enacted codes and standards to protect property and occupants in case of an earthquake. Learn about your area's codes before you begin construction.
If you are
inside when the shaking starts, you should:
• Drop, cover, and hold on. Move only a few steps to a nearby safe place. Most people injured in earthquakes move more ten feet during the shaking.
• If you are elderly or have a mobility impairment, remain where you are, bracing yourself in place.
• If you are in bed, stay there, hold on, and protect your head with a pillow. You are less likely to be injured if you stay in bed. Broken glass on the floor can injure you.
• Stay away from windows. Windows can shatter with such force that you can be injured
by flying glass even if you are several feet away.
• Stay indoors until the shaking stops and you are sure it is safe to exit. In buildings in the United States, you are safer if you stay where you are until the shaking stops. If you go outside, move quickly away from the building to prevent injury from falling debris.
• Be aware that fire alarm and sprinkler systems frequently go off in buildings during an earthquake, even if there is no fire. Check for and extinguish small fires, and exit via the stairs.
• If you are in a coastal area, drop, cover, and hold on during an earthquake and then move immediately to higher ground when the shaking stops. Tsunamis (large ocean waves) are often generated by earthquakes. (See “Tsunamis.”)
• Find a clear spot away from buildings, trees, streetlights, and power lines.
• Drop to the ground and stay there until the shaking stops. Injuries can occur from falling trees, streetlights, power lines, and building debris.
• If you are in a vehicle, pull over to a clear location, stop, and stay there with your seatbelt fastened until the shaking stops. Trees, power lines, poles, street signs, overpasses, and other overhead items may fall during earthquakes. Stopping in a clear location will reduce your risk, and a hard-topped vehicle will help protect you from flying or falling objects. Once the shaking has stopped, proceed with caution. Avoid bridges or ramps that might have been damaged by the quake.
• If you are in a mountainous area or near unstable slopes or cliffs, be alert for falling rocks and other debris that could be loosened by the earthquake. Landslides are often triggered by earthquakes. (See “Landslides.”)
the shaking stops, you should:
• Expect aftershocks. Each time you feel one, drop, cover, and hold on. Aftershocks frequently occur minutes, days, weeks, and even months following an earthquake.
• Check yourself for injuries and get first aid if necessary before helping injured or trapped persons.
• Put on long pants, a long-sleeved shirt, sturdy shoes, and work gloves to protect yourself from injury by broken objects.
• Look quickly for damage in and around your home and get everyone out if your home is unsafe. Aftershocks following earthquakes can cause further damage to unstable buildings. If your home has experienced damage, get out before aftershocks happen. Use the stairs, not an elevator.
• Listen to a portable, battery-operated radio or television for updated emergency information and instructions. If the electricity is out, this may be your main source of information. Local radio and television stations and local officials will provide the most appropriate advice for your particular situation.
• Check the telephones in your home or workplace. If a phone was knocked off its cradle during the shaking of the earthquake, hang it up. Allow 10 seconds or more for the line to reset. If the phone lines are undamaged, you should get a dial tone. Use a telephone or cell phone only to make a brief call to your Family Disaster Plan contact and to report life-threatening emergencies. Telephone lines and cellular equipment are frequently overwhelmed in disaster situations and need to be clear for emergency calls to get through. Cellular telephone equipment is subject to damage by quakes and cell phones may not be able to get a signal, but regular “land line” phones may work.
• Look for and extinguish small fires. Fire is the most common hazard following earthquakes. Fires followed the San Francisco earthquake of 1906 for three days, creating more damage than the earthquake.
• Clean up spilled medications, bleach, gasoline, or other flammable liquids immediately. Avoid the hazard of a chemical emergency.
• Open closet and cabinet doors cautiously. Contents may have shifted during the shaking and could fall, creating further damage or injury.
• Help people who require special assistance—infants, elderly people, those without transportation, large families who may need additional help in an emergency situation, people with disabilities, and the people who care for them.
• Watch out for fallen power lines or broken gas lines, and stay out of damaged areas. Hazards caused by earthquakes are often difficult to see, and you could be easily injured.
• Watch animals closely. Keep all your animals under your direct control. Pets may become disoriented, particularly if the disaster has affected scent markers that normally allow them to find their home. Pets may be able to escape from your house, and fencing may be broken. Be aware of hazards at nose and paw level, particularly debris, spilled chemicals, fertilizers, and other substances that might seem to be dangerous to humans. In addition, the behavior of pets may change dramatically after an earthquake, becoming aggressive or defensive, so be aware of their well-being and take measures to protect them from hazards, including displaced wild animals, and to ensure the safety of other people and animals.
• Stay out of damaged buildings. Damaged buildings may be destroyed by aftershocks following the main quake.
• If you were away from home, return only when authorities say it is safe.
When you return home:
• Be alert for and observe official warnings.
• Use extreme caution. Check for damages outside your home. Then, if the structure appears safe to enter, check for damages inside. Building damage may have occurred where you least expect it. Carefully watch every step you take. Get out of the building if you think it is in danger of collapsing. Do not smoke; smoking in confined areas can cause fires.
• Examine walls, floors, doors,
staircases, and windows.
• Check for gas leaks. If you smell gas or hear a blowing or hissing noise, open a window and get everyone out quickly. Turn off the gas, using the outside main valve if you can, and call the gas company from a neighbor's home. If you turn off the gas for any reason, it must be turned back on by a professional.
• Look for damage to the electrical system. If you see sparks or broken or frayed wires, or if you smell burning insulation, turn off the electricity at the main fuse box or circuit breaker. If you have to step in water to get to the fuse box or circuit breaker, call an electrician first for advice.
• Check for damage to sewage and water lines. If you suspect sewage lines are damaged, avoid using the toilets and call a plumber. If water pipes are damaged, contact the water company and avoid using water from the tap. You can obtain safe water from undamaged water heaters or by melting ice cubes. (See “Food and Water Safety During/Post Disaster”)
• Watch for loose plaster, drywall, and ceilings that could fall.
• Ask your community to adopt up-to-date building codes. Building codes are the public's first line of defense against earthquakes. National model building codes are available to communities and states. These codes identify construction techniques for buildings that help them withstand earthquakes without collapsing and killing people. Codes are updated regularly to make use of information learned from recent damaging earthquakes, so adopting and enforcing up-to-date codes are essential.
• If your area is at risk from earthquakes, ask your local newspaper or radio or television station to:
-Present information about how to respond if an earthquake occurs.
-Do a series on locating hazards in homes, workplaces, day care centers, schools, etc.
-Provide tips on how to conduct earthquake drills.
-Run interviews with representatives of the gas, electric, and water companies about how individuals should prepare for an earthquake. Help the reporters to localize the information by providing them with the local emergency telephone number for the fire, police, and emergency medical services departments (usually 9-1-1) and emergency numbers for the local utilities and hospitals. Also provide the business telephone numbers for the local emergency management office, local American Red Cross chapter, and state geological survey or department of natural resources.
• Work with officials of the local fire, police, and emergency medical services departments; utilities; hospitals; emergency management office; and American Red Cross chapter to prepare and disseminate guidelines for people with mobility impairments about what to do if they have to evacuate.